The primary goal of visualization is insight. An effective visualization is best achieved through the creation of a proper representation of data and the interactive manipulation and querying of the visualization. Large-scale data visualization is particularly challenging because the size of the data is several orders of magnitude larger than what can be managed on an average desktop computer. Data sizes range from terabytes to petabytes (and soon exabytes) rather than a few megabytes to gigabytes. Large-scale data can also be of much greater dimensionality, and there is often a need to correlate it with other types of similarly large and complex data. Furthermore the need to query data at the level of individual data samples is superseded by the need to search for larger trends in the data. Lastly, while interactive manipulation of a derived visualization is important, it is much more difficult to achieve because each new visualization requires either re-traversing the entire dataset, or compromising by only viewing a small subset of the whole. Large-scale data visualization therefore requires the use of distributed computing.